1. Field of the Invention
The present invention relates to a breath controlled air inlet for a blower and, particularly, to a shutter-type valve that opens and closes as a result of pressure changes in a facemask due to a user breathing while wearing the facemask.
2. Background of the Technology
Powered air supply systems are known in the industry for supplying air under pressure to a facemask wearer. Such systems are beneficial by providing a constant supply of air to the wearer as well as reducing the work that the wearer must perform when breathing in the air. However, the known powered air systems constantly supply air to the wearer without distinguishing between inhaling and exhaling by the wearer. Consequently, exhaling while wearing the facemask is known to become laborious, because the wearer must constantly overcome positive pressure from the air supplied by the powered air supply system, thereby tiring or fatiguing the wearer.
There also exists in the art a valve used in conjunction with the powered air supply system for controlling an amount of air fed into the facemask. One particular type of valve is illustrated in FIGS. 1(a) and 1(b). The valve 1 includes a housing 2, diaphragm 3, a spring 4, and a seal 5. The valve 1 is connected to an air inlet tube 7 at a first or inlet end and a facemask 6 at a second or outlet end opposite the first or inlet end. The air inlet tube 7 is connected to a powered air supply system (not shown). FIG. 1(a) illustrates a state wherein the wearer is not inhaling or breathing in air. Although the powered air supply system continuously creates a positive pressure and, hence, continues to supply air to the facemask 6, the diaphragm 3 remains in contact with the seal 5 because of a spring force provided by the spring 4. Once the wearer begins to breath in, pressure within the facemask 6 lowers, causing the diaphragm 3 to deflect, which compresses the spring 4, as illustrated in FIG. 1(b). As a result, air from the air inlet tube 7 flows through a gap created between the deflected diaphragm 3 and the seal 5 and into the facemask 6, as illustrated by arrows 8 in FIG. 1(b).
However, the known valve 1 requires a large diaphragm 3 and corresponding housing 2 in order to permit sufficient airflow into the facemask 6 because of the relatively small deflection of the diaphragm 3. Consequently, the size of the valve 1 is large, which hinders movement of the wearer's head and obstructs the wearer's vision. Moreover, new powered air supply systems must supply larger flowrates of air to the wearer, which further increases the size of the valve 1 and, correspondingly, the housing 2 of the valve 1. For example, many of the older powered air supply systems deliver approximately 120 liters per minute to the wearer. However, the new powered air supply systems must deliver approximately 300 liters per minute. Thus, the increase in size of the valve 1 creates an even larger obstruction to the wearer's vision. Therefore, the valve 1 is not capable of satisfactorily facilitating the increased flowrates required by the new powered air supply systems. As a result, there is a need in the art for a compact valve accompanying a powered air supply system that is capable of satisfactorily facilitating the increased flowrates required by the new powered air supply systems and that does not obstruct the wearer's field of view.
There also exists a powered air supply system having a blower operable at one speed when the wearer is inhaling and operable at a reduced speed at other times. However, the blowers of such powered air supply systems suffer from a lag or delay between the instant the wearer inhales and the instant the blower is capable of supplying air at a higher flowrate. During the lag period, an under-pressure situation occurs in the facemask, forcing the wearer to expend more effort to breathe. Over time, the extra effort causes fatigue to the wearer. The blowers of such systems also include a lag when transitioning to a lower speed when the wearer exhales. As a result, the wearer must exert extra effort to exhale against the pressure associated with the higher air supply level, which causes fatigue to the wearer.
Such systems also include lags associated with speeding up or slowing down a column of air traveling through a hose connecting the facemask and the blower. As a result, there is a need in the art for a compact valve that reacts quickly to inhaling and exhaling by a wearer and facilitates increasing flowrates required by new powered air supply systems as well as a valve that does not obstruct the wearer's vision or hinder movement of the wearer's head.